The goal of our research is to uncover the cortical computations that support the functions of the extrastriate visual areas of the cerebral cortex. Our approach is to create functional models of cortical processing, and fit them to data recorded from single neurons. Functional models are designed to account for the visual response properties of neurons as economically as possible. These models do not necessarily reflect the details of neuronal circuitry, but have an overall organization that is consistent with known structures and neuronal connections. We will focus our efforts on two important areas of extrastriate cortex, MT and V2. MT is a relatively small area that contains a high concentration of directionally selective neurons and is specialized for the analysis of motion information. V2 is the largest extrastriate area and its neurons have more diverse response properties. Both MT and V2 are heavily dependent on input from V1 for their visual responsiveness. To study processing in each area, we need to know the properties of the neurons that transmit information from V1, information that is available for MT, but not for V2. Our first aims are concerned with MT. First, we will extend an existing but limited functional model of MT to explain such essential features of neuronal responses as their dynamics, and their integration of motion information over space and time. The development and elaboration of this model will also form the basis for the subsequent development of models for visual responses in V2 and other extrastriate areas. Second, we will analyze the functional role of a major source of subcortical input to MT, the inferior pulvinar. We will identify and characterize pulvinar neurons that project to MT, and that receive input from MT, to elucidate the nature of MT's input-output relationship with this structure. Our second aims are concerned with V2. First, we will identify and characterize the V1 neurons that provide the major functional input to V2. With this knowledge and our experience with modeling MT, we will use a set of novel multi-component stimuli to build and evaluate a functional model of neuronal response properties in V2, with the goal of accounting for that area's responses to form and color information. The work proposed will advance the overall goal of understanding cortical computation in the visual system by bringing to bear on the extrastriate cortex a set of tools and methods that have had many signal successes in probing primary visual cortex function. PUBLIC HEALTH RELEVANCE Disorders of the visual nervous system are a major cause of visual disability, and many disorders affect parts of the brain outside the primary visual processing area of cortex, V1. Our research seeks to understand the function of cortical areas beyond primary cortex, where sensory data are transformed into signals that form decisions, guide actions, and create enduring memories of evanescent events.